Alkylation of hydrocarbons



Jan. 2, 1951 J. E. PENxcK ALKYLATION OF HYDROCARBONS Filed Sept. 28, 1948 Patented Jan. 2, 1951 ALKYLATION OF HYDROCARBONS Joe E. Penick, Woodbury, N. J., assignor to Socony-Vacunm Oil Company, Incorporated, a

corporation of New York Application September 28, 1948, Serial No. 51,572

3 Ciaims.

This invention has to do with the alkylation of hydrocarbons and, more particularly, has to do with the alkylation of hydrocarbons in the presence of hydrogen fluoride catalyst.

During the past decade, considerable progress has been made in the field oi alkylation, particularly with the development of improved automotive and Iaviation motor fuels. A leading development in this eld is hydrogen iluoride alkylation, wherein paraiiins are alkylated with olens in the presence of hydrogen iiuoride. This process generally involves contacting parafins, such as isobutane, with olens, such as nbutene, in the presence of hydrogen uoride, care being taken that a considerable excess of isobutane be used. In the reaction vessel, wherein the materials are contacted, alkylation of parain occurs. The reaction mixture of unreacted paraim, hydrogen uoride, alkylate and other hydrocarbon products, is taken from the reaction vessel to a settler, wherein separation of two layers occurs. The lower layer is predominantly hydrogen fluoride and the upper layer contains hydrocarbons saturated with hydrogen fluoride. From the settler, the upper layer is taken to an HF stripper wherein hydrogen iiuoride is removed overhead and the hydrocarbons are introduced to a central portion of a fractionating column, generally designated a deisobutanizer. Isobutane is removed as an overhead product from the deisobutanizer and alkylate, such as isooctane, is removed from the bottom thereof and is tenen to other fractionation means for separation of desired hydrocarbon fractions.

In the conventional hydrogen fluoride alkylation system briefly described above, it has been considered necessary to remove hydrogen uoride from the hydrocarbon layer taken from the settler. This makes necessary the use of a relatively large HF stripper in order to process the hydrocarbon layer which contains a large amount of isobutane together with alkylate products and other hydrocarbons. A second characterizing feature of the conventional system is the elective separation of isobutane from the hydrocarbon product taken from the HF stripper. It has been considered essential for eiicient operation to remove substantially all of the isobutane from the hydrocarbon product and this has been realized by introducing the hydrocarbon product .into an intermediate section of the deisobutanizer and returning a large proportion of isobutaue to the top of the deisobutanizer as reflux. As will be recognized by (Cl. 260-683A) those familiar with the art, the conventional process involves a considerable heat load upon the HF stripper in order to separate HF from the entire hydrocarbon product andV also involves a large heat input to the deisobutanizer so as to provide an effective separation of isobutane from the hydrocarbon product.

It has now been discovered that the foregoing process can be simplied with an appreciable reduction in heat requirements for the HF stripper and the deisobutanizer. The simplified process of this invention comprises introduction of the hydrocarbon product from the settler directly to an upper section of the deisobutanizer, dispensing with isobutane recycle thereto, and thereafter introducing the overhead from the deisobutanizer to a relatively small HF stripper.

In order to facilitate description of the process contemplated herein, reference is now made to the accompanying drawing, which shows a typical flow diagram of a preferred arrangement for practicing the invention. For convenience in illustrating the invention, the discussion of the process is directed specifically to alkylation of isobutane with butenes in the presence of concentrated HF. It will be understood, of course, that the invention is applicable also to alkylation of other hydrocarbons in the presence of HF.

Asshown in the drawing, an isobutane-butene charge in conduit i and HF in conduit 2 are combined and introduced into alkylator 4 through inlet 3. Alkylator i may be any suitable vessel resistant to corrosion by HF and provided with a mixing device, such as one or more jet-type and/or perforated plate-type inlets, baffles or stirrers, capable of maintaining liquid hydrocarbons and liquid HF in a state of intimate mixture. The relative proportions of HF and hydrocarbons, and the conditions of temperature and pressure in alkylator 4 are discussed hereinbelow.

The liquid reaction mixture in alkylator 4 is taken through conduit 5 to settler 6 wherein it separates into" two phases or layers. The lower layer is predominantly HF with a small amount of tar-like material. The HF layer is withdrawn from settler 6 through conduit 'l with the aid of pump 8 to HF regenerator 9. The tar-like material is separated in the regenerator 9 and is withdrawn through line lil. ,Regenervated HF is taken as an overhead through line Il and cooler l2 to line 1. Regenerated HF and HF in line 'l are returned to, the alkylator 4 through lines I2, Zand 3,

The upper layer in settler 6 contains alkyla- Vtion products, excess isobutane and may contain a small amount of propane and other hydrocarbons, and contains a small amount of HF, and is taken through conduit i3 to an upper section of deisobutanizer I4. The deisobutanizer I4 is operated to provide a rough fractionation of isobutane and alkylation products, with the latter beingv withdrawn from the bottom of the deisobutanizer I4 through conduit i5. It will be noted that the hydrocarbon layer from settler 6 is introduced directly to the deisobutanizer I4 at an upper section thereof and-that no recycle material is introduced at the top of the deisobutanizer to provide reflux therein; that is, there is no recycle reiux in the deisobutanizer. The alkylate withdrawn through conduit l contains some isobutane and can be concentrated in a fractionator (not shown).

A major proportion of the isobutane, propane the, are taken overhead from the deisobutanizer through conduit it, in which is located cooler i1', to accumulator i8. The material in accumulator i'is pumped through line l0 by means of pump 2Q. A major proportion, generally about 90%, of the material in line l5 is recycled through line 2li, with a minor proportion, generally about 10%, being introduced to H11 stripper 2-2.. .Tt-1FA and light hydrocarbons are removed as overhead in stripper 22, through line 23:, in which is located cooler 24, to .settler 25. 'I'.-wophases separate in settler 25, the upper phase comprising hydrocarbons and the lower phase HF. The upper phase is recycled to HF .stripper 2:2 through line 2t which connects with line l0. The lower phase, HF, isV taken through linefito recycle line 2 i. From the bottom of HF stripper 22,` a hydrocarbon fraction comprising Y propane5 isobutane and normal butane is removed through line 2.8. The latter hydrocarbon fraction, for example, may contain about 10 per cent propane, about 70 per cent isobutane and about 20 per cent normal butane.

To; demonstrate the advantages of the present process over conventional HF alkylation procedure, the following comparativey examples are set forth in Table I. In the conventional procedure, hydrogen fluoride was stripped from the hydrocarbon reaction product prior to introduction of the latter tov a deisobutanizer, which was operated under reflux. In the present process, the procedure described above and shown in the drawing was followed. To provide a proper comparative basis, the alkylaton conditions used were essentially the saine, with the same quantity, 11000 barrels per day, of alkylate of the same duality; 90.5 octane number, being produced. Conditions of operation were: ratio oi isobutane to butenes, 7:1; ratio of HF to hydrocarbon 1:1; 87 per cent HF; temperature and pressure of allrylator, 90 F. and 120 pounds per square inch; YContact time, 20 minutes.

l Expressed inV million B. t. u. per day.

Y reactions.

From the results shown in Table I, it will be noted that the saving, effected by the new process, in heat input to the deisobutanizer is 125 per cent, when the deisobutaniaer contains the same number of plates (50). There is a saving of 100 per cent in heat input, even when the number of plates is increased to in the conventional process. Y

Conventional alhylationconditions ottemperature, pressure, time, isoparaiiin-olein ratio and PEF-hydrocarbon ratio may be employed advantageously in the process contemplated herein. For example, the alkylation of isobutane with butenes may be carried out at temperatures between about 0 and 150 F., preferably between about 40 F'. and 140 F., at pressures at least sufficiently high to keep the hydrocarbons and HF in the liquid phase, and with isobutanebutene ratios of between 2:1 to 15:1, preferably etween about 6:1 and 10:1. Ratios of isobucbutenesfo at least 2:1 are'essentiaijisince ratiostend to cause polymerizationoiathe butenes with resultant decreaseY in yield` of; the alkylate product andi/or excess-ive reactonbctween the butenes and the primary alkylate f oroduict because of the relatively low ratios of isobutane 'to valkylate product in the reactiorrinixr ture. The HLT may be anhydrous orinay'have titratable acidity as low: as 70 per cent by weight, and is preferably between about' 804 to per cent. The ratio of HF to hydrocarbon eh ge may be -varied considerably, butmostsati` actory results are obtained with anexcessof Generally, ratios of to; hydrocarbon charge of at least 1:1are used., Reaction time is advantageously maintained between, abouti 1 minute and 60 minutes;

Wi'iile the process of thisinventic-n is particu.- larly weli adaptedfor the production of-Cs alli-111.- ates from isobutane and.v butenes, for example, the process is also suitable for other alkylation By way of illustration, C7 and Cs ali-zyiates may beprepared from isobutane and mixtures of propylene and: butenes; so. also, CQ alhylates may be obtained by alkylation of isobutane with pentenes. InV general', then, the process is suitable foralkylation of alliylatable particularly low-boiling isoparatwith alky-lating agents, particular y lowboiling olens. As a further illustration of' the` process, cunene may be prepared herein by re- -cticn of benzene with propylene.

claim:

1. The continuous process for alliylating, an alkyiatable hydrocarbon with an alkylating agent in the presence of hydrogen fluoride, which cornprises: contacting said alkyiatable hydrocarbon with said alkylating agent in an alkylator under alkylating conditions to form a' reaction mixture containing an alkylate of higher molecular weight than said alkylatable hydrocarbon; passing said reaction mixture to a settler wherein two phases are formed, one phase being essentially hydrogen fiuoride and theother phase being a hydrocarbon phase containing a small amount of hydrogen iiuoride, unreacted aikylatable hydrocarbon and said alkylate; separating said hydrogen fluoride phase andrecycl'ing the same to said alkylator; passing said hydrocarbon phase directly tothe top of a fractionator and fracticnating said hydrocarbon phase in the absence of reflux; withdrawing from the bottom of said fractionator a fraction containing sub,- stantially all of said alkylate and aA small; quan.- tity of saidVV unreacted alkylatable; hydrocarbon;

withdrawing from the top of said fractionator a fraction containing the bulk of said unreacted alkylatable hydrocarbon, a small amount ofgh'ydrogen fluoride and a small amount of said alkylate; recycling a major proportion of said last-mentioned fraction to the alkylator; fractionating a minor proportion of said last-mentioned fraction, removing a bottom product and recycling an overhead product of said unreacted alkylatable hydrocarbon and said small amount of hydrogen fluoride.

2. The continuous process for alkylating an isoparafln with an olefin in the presence of vhydrogen fluoride, which comprises: contacting said isoparaiiin with said olen and hydrogen fluoride in an alkylator under alkylating conditions to form a reaction mixture containing isoparaflins of higher molecular weight than said isoparan; passing said reaction mixture to a settler wherein two phases are formed, one phase being essentially hydrogen fluoride and the other phase being a hydrocarbon phase containing a small amount of hydrogen fluoride, unreacted isoparanin and said higher molecular weight isoparaiiins; separating said hydrogen iluoride phase and recycling the same to said alkylator; passing said hydrocarbon phase directly to the top of a fractionator and fractionating said hydrocarbon phase in the absence of reux; withdrawing from the bottom of said fractionator a fraction containing substantially all of said higher molecular` weight isoparaiiins and a small quantity of said unreacted isoparaln; withdrawing from the top of said fractionator a fraction containing the bulk of said unreacted isoparafhn, a small amount of hydrogen iluoride and a small amount of said higher molecular weight isoparafns; recycling a major proportion of said last-mentioned fraction to the alkylator; fractionating a minor proportion of said last-mentioned fraction, removing a bottom product and recycling an overhead product of said unreacted paraflin and said small amount of hydrogen fluoride.

3. The continuous process for alkylating isobutane with butenes in the presence of hydrogen iiuoride, which comprises: contacting said isobutane with said butenes and hydrogen uoride in an alkylator under alkylating conditions to form a reaction mixture containing isoparafllns of higher molecular weight than said isobutane; passing said reaction mixture to a settler wherein two phases are formed, one phase being essentially hydrogen fluoride and the other phase being a hydrocarbon phase containing a small amount of hydrogen fluoride, unreacted isobutane and said higher molecular weight isoparains; separating said hydrogen fluoride phase and recycling the same to said alkylator; passing said hydrocarbon phase directly to the top of a fractionator and fractionating said hydrocarbon phase in the absence of reux; withdrawing from the bottom of said fractionator a fraction containing substantially all of said higher molecular weight isoparans and a small quantity of said unreacted isobutane; withdrawing from the top of said fractionator a fraction containing the bulk of said unreacted isobutane, a small amount of hydrogen iiuoride and a small amount of said higher molecular weight isoparaiins; recycling a major proportion of said last-mentioned fraction to the alkylator; fractionating a minor proportion of said last-mentioned fraction, removing a bottom product and recycling an overhead product of said unreacted isobutane and said small amount of hydrogen uoride.

JOE E. PENICK.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number 

1. THE CONTINUOUS PROCESS FOR ALKYLATING AN ALKYLATABLE HYDROCARBON WITH AN ALKYLATING AGENT IN THE PRESENCE OF HYDROGEN FLUORIDE, WHICH COMPRISES: CONTACTING SAID ALKYLATABLE HYDROCARBON WITH SAID ALKYLATING AGENT IN AN ALKYLATOR UNDER ALKYLATING CONDITIONS TO FORM A REACTION MIXTURE CONTAINING AN ALKYLATE OF HIGHER MOLECULAR WEIGHT THAN SAID ALKYLATABLE HYDROCARBON; PASSING SAID REACTION MIXTURE TO A SETTLER WHEREIN TWO PHASES ARE FORMED, ONE PHASE BEING ESSENTIALLY HYDROGEN FLUORIDE, AND THE OTHER PHASE BEING A HYDROCARBON PHASE CONTAINING A SMALL AMOUNT OF HYDROGEN FLUORIDE, UNREACTED ALKYLATABLE HYDROCABON AND SAID ALKYLATE; SEPARATING SAID HYDROGEN FLUORIDE PHASE AND RECYCLING THE SAME TO SAID ALKYLATOR; PASSING SAID HYDROCARBON PHASE DIRECTLY TO THE TOP OF A FRACTIONATOR AND FRACTIONATING SAID HYDROCARBON PHASE IN THE ABSENCE OF REFLUX; WITHDRAWING FROM THE BOTTOM OF SAID FRACTIONATOR A FRACTION CONTAINING SU 